从 Python 中的子列表中获取元素

Question

I have a .csv file which contains the following 4 lines of elements:

dev1, NX-OS, 10.0.0.1, admin, admin
dev2, NX-OS, 10.0.0.2, admin, admin
dev3, NX-OS, 10.0.0.3, admin, admin
dev4, NX-OS, 10.0.0.4, admin, admin

I am trying to extract any of the elements. In order to do this, I've the following:

import csv
dev_list=[]
infile=open('dev_in.csv','r')
csv_in=csv.reader(infile)

for dev in csv_in:
    dev_list.append(dev)

The result out of dev_list is the following list of lists:

[
    ['dev1, NX-OS, 10.0.0.1, admin, admin'],
    ['dev2, NX-OS, 10.0.0.2, admin, admin'],
    ['dev3, NX-OS, 10.0.0.3, admin, admin'],
    ['dev4, NX-OS, 10.0.0.4, admin, admin']
]

In order to extract the first element of the first list, I coded:

element=dev_list[0]
print(element[0])

However, I'm getting the complete first list as a result:

dev1, NX-OS, 10.0.0.1, admin, admin

Maybe I should split it with the 'split' function but I think that would extend the code unnecessarily. What I need to extract the first elements of each sub-list. However, I may need later to extract other elements.

Is there another way? Is there also a better way to write this code, maybe with list comprehension Thanks in advance.

Answer 1

Summarizing my comment, here is what you need to do (with Python 3 in mind):

import csv
from pathlib import Path

dev_in = Path('dev_in.csv')

devs = list(csv.reader(dev_in.open(), skipinitialspace=True))

for dev in devs:
    # print dev names
    print(dev[0])

Code above will give the following lines as output:

dev1
dev2
dev3
dev4

Here is a proof of concept:

Python 3.7.5 (default, Dec 15 2019, 17:54:26) 
[GCC 9.2.1 20190827 (Red Hat 9.2.1-1)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import csv
>>> from pathlib import Path
>>> dev_in = Path('dev_in.csv')
>>> 
>>> devs = list(csv.reader(dev_in.open(), skipinitialspace=True))
>>> devs
[['dev1', 'NX-OS', '10.0.0.1', 'admin', 'admin'], ['dev2', 'NX-OS', '10.0.0.2', 'admin', 'admin'], ['dev3', 'NX-OS', '10.0.0.3', 'admin', 'admin'], ['dev4', 'NX-OS', '10.0.0.4', 'admin', 'admin']]
>>> dev=devs[0]
>>> dev
['dev1', 'NX-OS', '10.0.0.1', 'admin', 'admin']
>>> dev[0]
'dev1'
>>>

I hope it helps.